Create a data source name for the Access database in Control Panel->ODBC administrator. You can then connect to the database using $conn = odbc_connect("data source name", "username", "password").
You can query Access like such:
$q = "select field from table";
$results = odbc_do($conn, $q);
while(odbc_fetch_into($results, &$row)) {
$field = $row[0];
}
Good luck and don't expect much in the way of speed from Access.